The Las Vegas gunman who carried out the deadliest mass shooting in modern American history booked hotel rooms overlooking the Chicago music festival Lollapalooza, USA Today and ABC News report.

Stephen Paddock, who killed 58 people Sunday at a country music festival in Las Vegas, booked a room at the Blackstone Hotel room from Aug. 1 to Aug. 6 and another from Aug. 3 to Aug. 6. The checkout dates, as USA Today notes, correspond with the final day of the Lollapalooza festival, attended by tens of thousands of concertgoers, including Malia Obama.

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“We are aware of the media reports and have been in communication with our federal partners,” the Chicago Police Department told USA Today. “As you saw earlier this week the city conducts extensive public safety planning and training around major events, in close coordination with our law enforcement partners, to ensure public safety.”

ABC News and NBC News also report Paddock may have scouted sites in Boston.

Police don’t yet have a motive for why Paddock carried out the massacre, but Clark County Sheriff Joe Lombardo on Wednesday said investigators are operating under the assumption he had help with the attack.

“On face value, you have to make the assumption that he had to have some help at some point,” Lombardo said. “And we want to ensure that that’s the answer.”

Wednesday, the Las Vegas Review-Journal reported Paddock shot up two aviation fuel tanks near the concert venue, but “did not penetrate” the encasing, potentially sparing concertgoers and first responders from a “potentially massive explosion.”

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